Current microprocessor design trends include designs having an increase in power, a decrease in size, and an increase in speed. This results in higher power in a smaller, faster microprocessor. Another trend is towards lightweight and compact electronic devices. As microprocessors become lighter, smaller, and more powerful, the microprocessors also generate more heat in a smaller space, making thermal management a greater concern than before.
The purpose of thermal management is to maintain the temperature of a device within a moderate range. During operation, electronic devices dissipate power as heat that is to be removed from the device. Otherwise, the electronic device will get hotter and hotter until the electronic device is unable to perform efficiently. When overheating, electronic devices run slowly. This can lead to eventual device failure and reduced service life.
As computing devices get smaller (e.g., thinner), thermal management becomes more of an issue. Heat will be dissipated from a computing device by convection, conduction and radiation. For a forced convection computing device, it may include one or more fans used to move air through the computing device and cool one or more heat generating components of the computing device.
Thermal management systems may use sensors to track temperatures within the computing device (e.g., corresponding to heat generating components within the computing device) and increase a speed of one or more of the fans when a tracked temperature approaches a temperature limit of the corresponding component within the computing device. Once fan speeds reach limits, airflow through the computing device is maximized, and one or more of the heat generating components within the computing device are throttled. In other words, system performance is reduced to maintain all temperatures within the computing device within limits. Further, the fan consumes more power when operating at the increased speed, and the increased fan speeds create a noisier thermal management system from, for example, moving fan blades and motor spinning/vibration; this results in a noisier computing device.
System impedance is a parameter of the computing device that impacts both cooling capacity and system noise. The higher the system impedance, the less airflow the fans of the computing device may provide. Less airflow leads to higher component and skin temperatures. To obtain a same airflow in a first computing device (e.g., a high impedance system) compared to a second computing device with a lower system impedance (e.g., a low impedance system), higher fan speeds are needed. This results in higher system noise compared to the second computing device.